Wireless-telephone system.



L. DE FOREST.

WIRELESS TELEPHONE SYSTEM. APPLICATION FILED 11111.25. 1911.

1,183,803. Patented Maylfi, 1916.

UNITED sTArns PATENT OFFICE.

LEE m5: FOREST, 0!? NEW YORK, N. Y ASSIGNOB TO RADIO TELEPHONE & TELEGRAIH COMPANY, A-GORPOBATION OF DELAWARE.

WIRELESSPTELEPHONE SYSTEJIL.

Specification of Letters Patent.

Patented May 16, 1916.

Application filed January 25, 1911. Serial No. 604,566. g

- tems.

, the character referred to wherein map-v The object of the invention is to provide a transmitting apparatus for Wireless telephone systems wherein the articulation of transmitted voice sounds is made clear and distinct A further object is to provide a system of which balanced or inactive condition is dis-' turbed by and in accordance with sound waves, whereby corresponding high fre-- quency oscillations are impressed on the antenna system to effect the desired radiations.

Other objects of the invention will appear more fully hereinafter.

The invention consists substantially in the construction, combination, location, and relative arrangement of parts, all as will be more fully hereinafter set forth, as shown in theaccompanying drawings, and finally pointed out in the appended claims.

Referring to the accompanying drawings,

- and to the various views and reference signs appearing thereon,Fi-gure 1 is a view in diagram showing an arrangement of microphone for increasing the unbalanclng action due to impressing on the system the sound waves to be transmitted. Fig. 2 is a diagrammatic view showing an arrangement wherein the oscillations are produced in the antenna sys tem. Fig. 3 1s a view illustrating another arrangement of microphone connection embraced within the spirit and scope of my invention for increasing the unbalancing efi'ect of the sound waves to be transmitted. Inaccordance with the principles of my inventlon, and 1n the broad scope thereof, I

propose to associate a radiating antenna system with balanced or lnactlve clrcults in such relation that undernormal conditions no energy, or substantially none, is impressed upon the radiating antenna system' until the normal balanced condition thereof is disturbed, and I propose to disturb the normally balanced or inactive condition of said circuits by and in accordance with sonorous vibrations accompanying articulate speech or other sound, thereby impressing corresponding high frequency oscillations upon the radiating antenna system.

In carrylng out my invention I am enabled to employ an alternating or interrupted current source, having a frequency of alternations or interruptions below the upper limit.of audibility, thereby enabling me to use ordinary low frequency generators .or interrupters, and hence, to avoid the comphcations, expense and troubles incident to the designing and employment of high frequency generators.

The source of current may be associated with the balanced or inactive circuit system in many different ways, and various arrangements for such association are shown in the drawings as illustrative of practical methods of applications of my invention.

The desired unbalancing or disturbing effects and action may be secured in many dif-- ferent ways and various arrangements for accomplishing this result are shown in the drawings as illustrative of the principles involved. In practice, however, I- prefer to employ such an arrangement as will secure the greatest disturbance of the-balanced or inactive condition. a

As above indicated I propose to employ a source of alternating or interrupted current. I have shown. an alternating current generator S, as an illustrative arrangement. The source of current is associated with the balanced or inactive circuit system, presently to be described, preferably through a step up transformer I have found that a source of the current source is associated inductively through the step-up transformer with an oscillating circuit in WhlCll a discharger D, and an inductance P, are in series with a capac1ty C,'br1dged across their terminals. By reason of the association of the circuit of alternating or interrupted current withthe oscillating circuit, above described, oscillations are developed in the oscillating circuit in a well understood manner. It is immaterial whether the capacity C bridges the terminals of the discharger and inductance P, the latter being in series in the oscillating circuit, or instead, the relative locations of the discharger and capacity 7 be interchanged.

The circuit of the current source may be inductively associated with the oscillating system, as shown in Fig. 1, or 1t may be directly connected thereto, as indicated in Fig.

3, and it is obvious that any other well known form of coupling may be employed.- The same is true of the coupling of the OSClllating circuit with the balanced or inactive circuit System. In Fig. .1, I have shown the oscillating system associated with the balanced circuit system through a conductive coupling, the inductance P, in this case being common to both the --oscillat1ng and the .balanced circuit systems.

Any desired form of discharger D, may be employed, such for instance, as the slnglng spark radiotone system, indicated at D, m Figs. 1 and 3, or an ordinary spark discharge gap. In the case of the radiotone gap the. electrodes are in the form of disks or plates of metal, superposed upon but separated from-each other sufiiciently and in such manner as to leave air-tight spaces therebetween, in the usual manner. Inthe case of the ordinary spark discharge gap the electrodes may be of carbon or in the form of metal balls. While I prefer to employ the quenched spark gap of the radiotone form for the reason that thereby the high frequency oscillations in the oscillating circuit are strongly damped, and there is no reaction of the oscillations in the. antenna, or balanced circuit systems, upon the oscillating circuit, still the ordinary spark gap I has certain' advantages as the are therebetween establishedallowsra large number of discharges per half cycle, thereby --which would cause to cease,

rendering the voice sounds as received at the receiving station less disguised or m'u-' tilated by the hum or whistling sound, which might accompany the same if the normal balance or inaction of the bridge circuit system should be more or less imperfect.

By'choosing condensers of small capacity and making the spark gap spaces small in extent, I am enabled to secure a.very large number of partial discharges of the condcnsers'for each half period of current, particularly if the impressed voltage is relatively large. A I

-I have found it desirable to insert a considerable inductance in the current supply circuit, as indicated at I, which I propose to make adjustable, so that I may be able to employ short discharge gaps and small capacity without establishinga non-oscillat mg gap across the gap, the existence of or to greatly weaken, the partial discharges.

Where the coupling of the oscillating circuit to the balanced circuit system is conductive, as through an auto-transformer, as indicated in Figs. 2 and 3, the coupling coil P, is connected in series to the balanced circuit system.

antenna A, being connected to the balanced circuit system at a, and the earth connection E, thereof belng connected to the balanced system at I), while the terminals of the transformer coil L, or auto-transformer coil P,

as the case may be, are onnected to the balanced circuit system at the points 0 and d. In the arrangement shown in Fig. 1, each of the legs 1 and 2 of the balanced circuit system contains a capacity, as indicated at C C one or both of which may be variable, and the legs 3 and '4, respectively contain the inductances L L one or both of which may be variable. By reason of, the presence of the capacities and inductances in the balanced circuit systems this circuit system has a natural period of vibration of its own. The electrical constants of this balanced cir-' cuit system should be so chosen that said system is in resonance with the primary oscilso relatively proportioned that, normally, no difference of potentialexists between the points a, and b. In this condition, therefore, no current is impressed upon the antenna system and the balanced circuits are inactive. When'the balance of these normally inactive circuits isdisturbed, however, as by so varying the inductances L or "L or the capacities C, C one or more, that the ratio 10 reactance of leg 3 reactance of leg 1 reactance of leg 4 reactance of leg 2 equals no longer exists, a potential difference be-- more or less intense according to the degree of disturbance of the ratio referred to.

Various-means and arrangements may be employed .for eflecting the disturbance of the normally balanced inactive circuits, within the spirit and scope of my invention, and in .the case of the use of the apparatus for telephonic transmission purposes I propose. to efi'ect such disturbance by and in accordance with the sound waves which accompany articulate speech or other sound, so as to not only impress upon the radiating system resulting oscillations but a-lso, so as to impress such oscillations which are varied in intensity according to the sound waves employed in effecting the disturbance of the balances In other words, the balance of the normally inactive circuit system is disturbed by and in accordance with sound waves, and the radiations from the antenna system conform in intensity to the degree ofsuch disturbance.

A convenient and eflective method for accomplishing the unbalancing of the normally inactive circuit system is to connect a microphone in shunt around or in series with one ofthe impedances. haveshown a microphone M connected in shunt around the inductance L and I have found that better results are attained'iby associating the microphone with an inductance instead of with a capacity. The

balance of the system may be still more effectively disturbed by employing two microphones, one associated with the inductance ineach of the two legs of the system which contain inductances, with the microphones so connected up that the resistance of the one will be increased while that of the other is simultaneously decreased by the same sound waves impinging thereon. Fig. 1 shows such an Here the diaphragm F 18 acted upon by sound waves directed thereto arrangement.

through the mouth piece of the microphone M. This diaphragm is rigidly connected to a button' diaphragm V, on both sides of which are carbon granules contained in in- -.ul:|=c(l chambers in the casing B. 'lhe back an inductance L In Fig. 1 I.

or end wall of one chamber is connected to the remote terminal or end'of inductance L, in leg 3, while the back or end wall of the other chamber is connected to the remote terminal or end of inductance L in leg 4. The proximate ends or terminals of the inductances are connected from their common point Q, to the vibrating member V. In this arrangement it will beseen that the resistance of the carbon granules in one chamber is increased simultaneously with a corresponding decrease in resistance of the granules in the other chamber, and this respective increase and decrease is accomplished by the same sound waves impinging on the diaphragm F. Thus the disturbing effect on the balance of the normally inactive circuit system is doubly amplified. It is obvious that various other methods of securmg the balanced condition between the di erent legs or branches of the system, or of simultaneous effects of two separate circuitsupon a third. circuit will at once suggest themselves to persons skilled in the art,

corresponding radiations 'efiected from, the

antenna system.

.A variation of the same. general principlcs as above set forth is shown in Fig. 2. Here the balanced circuits are bridged by a circuit connecting the points a, and b, the antenna A, being connected to earth at E, through this bridge circuit. Also arranged in this bridge circuit is the spark cap D which .is shunted by a condenser C and Each of the legs or branches 1, 2, 3, 4, contains an inductance L, and each inductance is shunted 'by a microphone M In this case, also, the current source S, is coupleddirectly to the balanced circuit system without the interposition of an oscillating circuit, the coupling, in this instance, being shown as inductive through the transformer coils T. Consequently the balanced circuit branches are traversed by alternating or interrupted, currents -of low frequency, say 50 to 500 cycles, or higher if desired, as distinguished from the higher frequency or Hertzian currents which traverse the balanced circuit system in the arrangements shown in Fig. 1. In the arrangement shown in Fig. 2 all of the inductances L should be oflarge value as compared with those employed in the arrangements of Fig. 1. Thus in the latter case the inductance coils are preferablywound without iron cores. while the coils .L, of the arrangement of Fig. 2 are preferthis arrangement do not contain capacity, for, if capacities were employed they would be required to be of very large value, say, of the order of microfarads. The balance of the circuits in this arrangement shown in Fig. 2 may be secured by suitably adjusting one or more of the inductances L, in the, legs or branches 1, 2,3,. 4. This may be accomplished by making the laminated cores of the inductance coils movable and inserting, or withdrawing the same, more or' less, into or from the coils. When the balanced condition is attained by suitable adjustment of the inductances, no difference of potential, or practically none, will ordinarily, or normally, exist across the terminals of the spark gap D This spark gap should be small in this case. While I have shown a microphone shunting each inductance L, I do not desire to be limited in this respect. Where four microphones are employed I prefer to actuate the diaphragms thereof simultaneously by sound waves delivered thereto through a mouthpiece common to all of them, and in order to amplify the unbalancing effect of the sound vibrations upon the normally inactive circuit system, I prefer to so arrange the microphone diaphragms in relation to their associated inductances as to increase the resistance in two of the legs or branches, say the legs or branches 1 and 4, while simultaneously reducing the resistance in the other legs or branches 2, 3. With this arrangement the balance of the bridge is greatly disturbed by the action of the sound waves impinging on the microphone diaphragms and considerable difference of potential will be instantaneously developed across the spark gap D and an oscillatory discharge will take place thereacross and in the circuit L, C D the intensity of the discharges being governed by the degree to which the bridge balance has been disturbed. In Fig. 3 I have shown one arrangement of the four microphones of Fig. 2, so connected and associated with their respective inductance coils that the resistance in legs or .branches 1 and 4 is increased simultaneously withv a decrease of the resistance in the legs or'branches 2 and 3.

It will be understood that in any of the various arrangements shown the inductances may be replaced by resistances, but this is not recommended on account of losses of energy due to the heat developed in resistance coils. v

The arrangement shown inFigs.2 and 3, possesses the advantage that the receiving apparatus associated with the generating and radiating apparatus at a transmitting station is not acted upon in any way by such transmitting apparatus except during the time the transmitter diaphragms are being actually operated by sound wavesimpinging thereon. This enables me to attain to and fro conversation without the necessity of switching over from sending to receiving.v I have shown a typical receiving circuit arrangement suitably (oupled, in this instance inductively, with the tuning coil L in the antenna clrcuit, through an inductance coil L. The receivin circuit shown includes the telephone receiver T the detector D when the balanced or normally inactive condition of the circuit system associated therewith is disturbed, and, when such disturbance iseflected, the radiating system is supplied with energy the intensity of Which varies according to the degree of such disturbance, and hence by employing voice or other sounds to effect the balance disturbance, radiations are secured which carry variations in intensity imposed by and in accordance with sound waves. By this arrangement I am enabled to secure a much greater degree of variation in the intensity of the radiations than has heretofore been possible in wireless telephonic work, and hence am enabled to secure sharper, clearer and more distinct articulation in the receiving apparatus, and am enabled to employ low frequency generations or interruptions as the source of primary current, thereby eliminating many of the complexities and difiiculties which have heretofore attended the use of high frequency generators for use in this class of work, besides greatly simplifying the apparatus and circuit arrangements, and eliminating many of the delicate adjustments heretofore required in maintaining wireless telephone systems in opera tive conditions.

Having now set forth the object and nature of my invention and various embodiments of the principles thereof, what I claim as new and useful, and of my own invention, and desire to secure by Letters Patent is,-

1. Anantenna system, a source of energy therefor, a circuit system interposed between the source of energy and the antenna system, said interposed circuit system. being normally balanced to restrain the impression of the balanced condition'l of said circuit system, and means for amplifying the balance said branches or legs, to amplify a disturbance of the balanced condition of said circuit system.

In testimony whereof I have hereunto set my hand in the presence of the subscribing 15 witnesses, on this 7th day of January, A. D., 1911.

LEE on FOREST.

Witnesses:

R. W. MoELRoY, EDITH W. BURNHAM. 

